Characterization of multi-interface, multi-layer heavily doped Si:P nanostructures using electromagnetic propagation

摘要

Layered semiconductor structures like delta-dopings and buried amorphizations, where modified optoelectronic features result simultaneously from material composition and from device design, can considerably widen optoelectronic applications of conventional materials. Multi-interface novel devices (MINDs) based on a nanoscale Si-layered system buried within the heavily P-doped Si wafer have an unusual reflection, absorption and internal light propagation, which can be dominated by a dense free-carrier gas confined within a surface potential well. First, a model of optical functions of the heavily doped Si:P using experimental data published previously for extremely heavily P-doped Si using the Transition Matrix Approach (TMA) to simulate the electromagnetic optical response and field propagation has been constructed. The dielectric function combines oscillation functions and a dense free-carrier gas (Lorentz-Drude approach) and can take into account an inhomogeneous P-doping distribution. Next, an optical model of the real multi-interface device, based on electron microscopy data, has been constructed. A simplified sequence of buried, optically active interfaces and corresponding layers (with transformed material and refraction indexes) is possible due to a planar geometry. Finally, we compare our simulated and experimental reflectivity. In this way we could determine particularly difficult-to-measure parameters. The method presented could be useful for device characterization during the fabrication